MALIBU, Calif. — The battle between Malibu beachfront homeowners and a less privileged public who want to share the stunning coastline has been fought with padlocks, gates, menacing signs, security guards, lawsuits and bulldozers. There seems little question who is winning: 20 of the 27 miles of Malibu coastline are inaccessible to the public.

Yet this month, the homeowners — including some of the wealthiest and most famous people in the country, and a hearty colony of surfers, stoners and old-fashioned beach lovers — are confronting what may be the biggest threat to their privacy yet.

The smartphone.

Jenny Price, an environmental writer who has pressed the battle to open hidden beaches, developed an iPhone app offering a beach-by-beach battle plan for anyone wishing to explore what are, by design, some of the most secluded beaches around. It has maps to often hidden entry gates, house-by-house descriptions showing public property boundaries and spine-stiffening advice on dealing with counterfeit no-parking signs (“feel free to enjoy and then ignore”) and threatening property owners (“they're welcome to call the sheriff”).

This latest escalation in a seemingly never-ending battle is stirring questions of land use, property rights and privilege that have long been a source of tension in Southern California, a fight made all the more alluring because long stretches of beachfront are owned by well-known Hollywood figures, including David Geffen, Michael D. Eisner and Jeffrey Katzenberg.

By state law, California beaches are public property, though the dividing line between private property and public beach is as changeable as the high-tide mark and the easements a homeowner is granted for development rights. And the beachfront homes in Malibu tend to be crammed together, making it impossible to catch even a glimpse of long stretches of the beach, much less walk onto it.

“I sort of see this as one of the most egregious problems we have with public space in a region that's plagued with problems with public space,” Price said as she walked along Carbon Beach, lined with glistening estates, the only sign of life being the clip-clip-clip of the occasional landscaper.

Later, strolling along Malibu Road Beach as the sun cracked through the morning marine layer, Price stopped in front of a house that had seven variations of a “no trespassing” sign. “You need to stand behind the tide line,” she said. “Last time we were here, the owner called the sheriff.”

The release of the “Our Malibu Beaches” app has set off waves of anxiety among homeowners here, fearful that a high-tech weapon in a long-fought war will open the gates on what has been a largely secret world. The despair cuts across demographic lines. Malibu is a more complicated place than is commonly portrayed, a mixture of the very wealthy and people who bought relatively modest homes and cabins here a generation ago and hung on.

“There are plenty of places that have bathrooms, lifeguards, parking,” said Wendy Ledner, who grew up on Malibu Road Beach. “There are none of those facilities at these beaches. People come through, they urinate, defecate, they leave their garbage — there are no garbage pails. They can't park; there is no parking, so they block driveways.”

Arnold G. York, publisher of The Malibu Times, said the uproar was feeding long-held and incorrect stereotypes about the community. “One of the things that makes for a wonderful story is how Malibu is elitist and we don't want anyone here,” he said. “The reality is we get 15 million people coming out each year to the beaches. The biggest problem is not access but parking.”

He said he understood the concern of homeowners that these remote and often small beaches, some with rough surf and jagged rock formations, were not made to accommodate large influxes of sun-seekers.

There are 17 public access ways to the Malibu coastline. Under state law, there should be more than 100. The last time one was opened was in 2005.

“There is a lot of resistance to opening new access ways; there are 15 additional easements that have yet to be opened,” said Linda Locklin, who leads the coastal access program for the California Coastal Commission. “Our record is frankly not so good. It takes us forever to open them.”

Much of the information in the Malibu beach app has been available to the public, but in the form of bulky, 300-page regional coastal guides, which cost $25 apiece.

Locklin called the app “a big deal” that would greatly advance the commission's goal of making these beaches more accessible. It is easier to use than the books and, at least for now, free. (An Android version of the app is expected to be released in the fall and cost $1.99.)

This tug of war has always had overtones of class warfare. One of the beaches is known as Billionaires' Beach, and Price has named the access way to that beach “Hurray for Hollywood.” Still, she said she resisted any attempt to frame the battle along those lines, even as she stood in front of the home of Geffen, who at first fought the coastal commission when it tried to open a public walkway by his home.

“It's not a take-down-the-billionaires project,” Price said. “This is not a political statement. People are constantly asking us, 'Can you show us Pierce Brosnan's house?' Yeah — but no.”